Open source software licenses can be used for non-software works, and often are the best choice. This is particularly the case when the works in question can be edited and versioned as source, e.g., open source hardware designs. Choose an open source license.
Any open source software license or open license for media (see above) is applicable to software documentation. If you use different licenses for your software and its documentation, you may wish to take care that source code examples in the documentation are also licensed under the software license.
The SIL Open Font License 1.1 keeps fonts open but allows them to be freely used in other works.
If your project contains a mix of software and other material, you can include multiple licenses, as long as you are explicit about which license applies to what parts of the project. See the license notice for this site as an example.